The present invention relates to safety equipment, and in particular, to a magnetic latch and switch combination highly resistant to generating false “door closed” signals and that may be flexibly employed in a variety of safety situations.
Many industrial processes present risks to human operators during one or more operating phases. These risks may be reduced through the use of “safety systems” which provides specialized computers and sensors that help ensure the safety of human operators in such environments.
The safety system may monitor operation of the industrial process and detect risk to human operators within a risk zone at certain times during that process by monitoring or controlling the position of the human operators through the use of various sensing systems and barricades. Common sensor systems include pressure mats and light curtains. Highest security is provided by mechanical barriers, such as gates having switches indicating whether the gate is open and access to the risk zone is possible.
In the latter case, it is important that the switches on such gates be highly resistant to failures that incorrectly indicate that the gate is closed when the gate is open, whether the failure is caused by normal wear, damage, environmental contamination, or tampering.
One method of producing such reliable switches employs a “radio-frequency identification” RFID tag positioned on one component of the gate and an RFID tag sensor on another component of the gate, such that the sensor and tag are separated when the gate is open. Positive indication of gate closure requires not only detection of proximity of the RFID tag (which may only be sensed at close ranges) but that a numeric code embedded in the RFID tag be the correct numeric code for the gate, preventing tampering through the use of different RFID tags.
Ideally, this RFID sensor system might be incorporated into a latch used to hold the gate closed to be automatically positioned near to elements of the gate which separate when the gate is opened. The wide variety of different types of latches intended for gates of different sizes dimensions and operation, make incorporating an RFID sensor system into the latch difficult.